Current aircraft engine actuation loops use fixed pressure levels of fuel to provide a required force for actuation purposes. These fixed pressure levels are generated using pressure regulators. This is an inefficiency in the system due to the pressure loss from pump discharge down to the regulated supply pressure.
The use of fuel on aircraft engines to drive actuation loops is common. These actuation loops are typically supplied from one or more regulated pressure sources and referenced to the low pressure stage of the fuel pump, commonly a centrifugal stage. The need for a fixed differential pressure, provided by pressure regulators, is driven by control needs to avoid large changes in control gains. In order to generate these fixed pressure differentials, discharge pressure from the pump is regulated or allowed to leak through a valve, or pressure regulator. This leakage is an inefficiency in the fuel system.